The structural and regulatory sequences within SV40 and adenovirus 2 DNA, expressed early and late in infection will be precisely mapped, using both linked transcription-translation cell-free systems and hybrid arrested translation. DNA sequences coding for specific information then will be correlated directly with their corresponding messenger RNAs. These precise coordinates of coding and non-coding regions within DNA will be compared directly to those of the RNA splicing in order to ascertain the possible function of this precise mapping data will be used in the construction of experiments to study the regulation of differential gene expression during viral infections and also viral induced alterations of host cell functions.